Process for preparing a mixture of amino-containing phosphazenes

ABSTRACT

The present invention provides a process for preparing a mixture of amino-containing phosphazenes having the following general formula (I) by reacting a (NPCl 2 ) n  phosphazene mixture with NH 3  and HOR in the presence of a tertiary amine catalyst: 
     
       
         N n P n (NH 2 ) x (OR) 2n−x   (l) 
       
     
     wherein n≧3, 1≦x&lt;2n, and R is phenyl or C3-C6 alkyl. In addition to simultaneously carrying out amination and esterification, the process of the present invention also simultaneously performs a regeneration of the catalyst. Furthermore, the invented process is a water-free process without the problem of a large quantity of waste water. Ammonium chloride, a by-product of the invented process, can be recovered in a subsequent process.

FIELD OF THE INVENTION

The present invention relates to a process for preparing a mixture ofamino-containing phosphazenes that can be used simultaneously as acuring agent and a flame retardant for resins, particularly to awater-free process for preparing an mixture of amino-containingphosphazenes.

BACKGROUND OF THE INVENTION

Phosphazenes are compounds that contain —P=N— bonds and have a generalformula [NPR′R″]_(n), wherein n is ≧3. Such compounds have thousands ofderivatives along with a change in R′ and R″. In addition to a variationin R′ and R″, the structures of the phosphazenes can be classified intocyclic compounds and linear compounds. When n=3, the compounds becomebenzene-like hexagonal planar compounds. When n=4, the compounds becomeoctangular cyclic compounds. Among the identified cyclic phosphazenes,the maximum n value is 10. Phosphazenes with n≧3 can also exist in alinear form. Phosphazenes have always been viewed as a potential flameretardant in view of a synergistic effect of P and N elements. When R′or R″ is a group containing an active hydrogen (such as amino orhydroxyl), such phosphazenes can even be used to cure a resin havingfunctional group(s) that can react with an active site, such aspolyurethane having isocyanate terminals and epoxy resins. A typicalexample of the amino-containing phosphazene that can be used as a curingagent and a flame retardant for the polyurethane and epoxy resins, has astructure of N_(n)p_(n)(NH₂)_(x)(OR)_(2n−x), wherein 1≦x<2n, and R isphenyl or C3-C6 alkyl. The conventional processes for preparing suchamino-containing phosphazenes basically can be classified into twotypes. The first type of preparation process comprises amination andthen esterification; and the second type of preparation processcomprises esterification and then amination. The following Scheme 1shows an example of the first type, in which N₃P₃(NH₂)₂(OC₃H₇)₄ issynthesized:

In Scheme 2, the amination step can only be completed under apressurized state, which increases the complexity and the safetyconcerns of the process.

The above-mentioned processes all have a defect of having too manyoperational steps thereof. Take Scheme 1 as an example:

Step 1: amination;

step 2: separating the organic phase from the aqusous phase after theamination;

step 3: removing the organic solvent by evaporation, thereby obtainingN₃P₃(NH₂)₂Cl₄;

step 4: reacting the intermediate product N₃P₃(NH₂)₂Cl₄ with NaOC₃H₇under refluxing;

Step 5: after reaction, washing off NaCl with water; and separating theorganic phase from the aqueous phase;

Step 6: drying off residual moisture in the organic phase; and

Step 7: removing the organic solvent from the organic phase byevaporation, thereby obtaining the product.

SUMMARY OF THE INVENTION

The present invention provides a process for preparing a mixture ofamino-containing phosphazenes having the following general formula (I)via simultaneous amination and esterification by reacting a (NPCl₂)_(n)phosphazene mixture with NH₃ and HOR in the presence of a tertiary aminecatalyst:

N_(n)p_(n)(NH₂)_(x)(OR)_(2n−x)  (l)

wherein n≧3, 1≦x<2n, and R is phenyl or C3-C6 alkyl.

In addition to simultaneously carrying out amination and esterification,the process according to the present invention also simultaneouslyperforms a regeneration of the catalyst. Therefore, the invented processnot only greatly reduces the operational steps, but also the reactiontime. Moreover, the invented process is a water-free process without theproblem of a large quantity of waste water and sodium chloride.Furthermore, a by-product, ammonium chloride, of the invented process,can be recovered in a subsequent process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a reaction system suitable for use inthe invented process.

DETAILED DESCRIPTION OF THE INVENTION

The present invention discloses a process for preparing a mixture ofamino-containing phosphazenes having the following formula (I):

N_(n)P_(n)(NH₂)_(x)(OR)_(2n−x)  (l)

wherein n is an integer and n≧3;

x is an integer of 1≦x x<2n; and

R is phenyl or C₃-C₆ alkyl, preferably R is propyl.

Said process comprises the following steps:

a) introducing NH₃ into a reactant mixture comprising HOR, mixedphosphazenes of (NPCl₂)_(n) and a tertiary amine to undergo reactions ata temperature of 30-100° C. for a period of time;

b) removing a solid comprising NH₄Cl precipitate from the resultingreaction mixture from step a) by a solid-liquid separation means; and

c) removing volatile compounds from the resulting liquid from step b) byevaporation to obtain a mixed product consisting essentially ofamino-containing phosphazenes having the formula (I).

Preferably, the reactant mixture used in step a) of the invented processfurther comprises an organic solvent, preferably chlorobenzene.

Preferably, the mixed phosphazenes of (NPCl₂)_(n) in step a) comprise60-70% by mole of phosphazenes where n=3; 10-20% by mole of phosphazeneswhere n=4; and 10-20% by mole of phosphazenes where n≧5.

Preferably, the tertiary amine in step a) of the invented process ispyridine.

Preferably, the reactant mixture in step a) of the invented processcomprises 100-500 parts by weight of phosphazenes, 20-150 parts byweight of pyridine, and 500-2000 parts by weight of HOC₃H₇. Morepreferably, said mixture comprises 350 parts by weight of phosphazenes,40-80 parts by weight of pyridine, and 1000 parts by weight of HOC₃H₇.

When the reactant mixture of step a) further comprises chlorobenzene,said reactant mixture of step a) preferably comprises 100-500 parts byweight of phosphazenes, 80-360 parts by weight of pyridine, 300-2400parts by weight of HOC₃H₇, and 500-3600 parts by weight ofchlorobenzene. More preferably, the reactant mixture of step a)comprises 350 parts by weight of phosphazenes, wherein the part byweight of chlorobenzene is not less than that of HOC₃H₇.

The present invention will be further disclosed through the followingexample. The example is for illustrative purposes only and not forlimiting the scope of the present invention.

EXAMPLE

In this example, the reaction for the synthesis ofN_(n)P_(n)(NH₂)_(x)(OC₃H₇)_(2n−x) can be shown by the following:

since the product is to be used for the curing of epoxy and polyurethaneresins, each molecule needs to have at least two NH₂ groups. Because thesynthesized product is not a single amino-containing phosphazene, suchas a pure N₃P₃(NH₂)₂(OC₃H₇)₄, but is a mixture ofN_(n)P_(n)(NH₂)_(x)(OC₃H₇)_(2n−x). Therefore, this example will show theeffect of reaction conditions on the x value.

This example uses a reaction system, as shown in FIG. 1, which comprisesa reaction bottle G placed on a thermostat H. Said reaction bottle G isequipped with a thermometer insertion tube A, a feed tube B, amechanical stirrer C, a said condenser D. Said an inlet tube for NH₃gas, wherein an NH₃ gas cylinder J is connected to said inlet tube forNH₃ gas and a washing tower E is connected to said condenser D. Saidinlet tube for NH₃ gas is installed with a needle valve I for flowcontrol and a flow meter F.

Pyridine (abbreviated as Py hereinafter), chlorobenzene (abbreviated asCB hereinafter), n-Propanol (abbreviated as NPA hereinafter) were fed tothe reaction bottle G according to a predetermined stoichiometric ratio.A phosphazene mixture of (NPCl₂)_(n) (consisting of 60-70% by mole ofphosphazene where n=3; 10-20% by mole of phosphazene where n=4; and10-20% by mole of phosphazene where n≧5) was added within 30 minutes.The temperature of the reaction liquid is maintained at 25-35° C. Uponcompletion of the addition of (NPCl₂)_(n), an NH₃ gas was introducedaccording to predetermined flow rates, and the thermostat was used tomaintain the reaction temperature according to the following schedule:

Stage one 40° C. 2 hours Stage two 50° C. 2 hours Stage three 60° C. 2hours Stage four 70° C. 1 hour

Upon completion of the reaction, the introduction of NH₃ was stopped,and the reaction mixture was allowed to cool down to room temperaturewithout disturbance. Then, the solid ammonium chloride was filtered out,and the liquid part was subjected to removal of Py, CB and NPA byevaporation at a temperature of 90° C. and a pressure of 30-40torr,thereby obtaining a brown product.

The amination and esterification of the reaction mixture were monitoredby using IR spectrum. The results show that the substituents of —NH₂ and—OC₃H₇ absorption peaks appeared within the first hour after thecommencement of the reactions. This indicates that the reactions of theesterification and amination take place simultaneously. The relativepositions of the absorption peaks of the two substituents do not varymuch after four hours of reaction, which indicates that the mainsubstitution reactions have been completed.

N_(n)P_(n)(NH₂)_(x)(OC₃H₇)_(2n−x) contains —NH₂ and —OC₃H₇ groups, andshows IR absorption peaks of ν N—H 3270cm⁻¹ and ν-C—H 2965cm⁻¹,respectively. The intensities of the absorption peaks are related to xand 2n−x values. A larger x value indicates a larger amount of —NH₂groups present, and vice versa. Therefore, the ratio of the twoabsorption peaks can be used to estimate the degree of amination. Table1 shows elemental analysis of the related amino- containingphosphazenes.

TABLE 1 Molecular formula MW P % Cl % C % H % N % N₃P₃(NH₂)₁(OC₃H₇)₅ 44620.85 0 40.35 8.30 12.55 N₃P₃(NH₂)₂(OC₃H₇)₄ 403 23.08 0 35.73 7.94 17.37N₃P₃(NH₂)₂(OC₃H₇)₃Cl 379.5 24.50 9.35 28.46 6.59 18.40N₃P₃(NH₂)₃(OC₃H₇)₃ 360 25.83 0 30.00 7.50 23.33 N₃P₃(NH₂)₃(OC₃H₇)₄Cl336.5 27.64 10.55 21.39 5.94 24.96 N₄P₄(NH₂)₂(OC₃H₇)₆ 566 21.91 0 38.168.13 14.84 N₄P₄(NH₂)₃(OC₃H₇)₅ 523 23.70 0 34.42 7.84 18.73

Table 2 lists the influence of the flow rate of NH₃ gas, the amount ofCB solvent, and the amount of Py on the degree of amination of theproduct.

TABLE 2 Ratio of IR absorption Flow rate of peaks of Run Py NPA CBNH₃*time NH₂/OC₃H₇ P% Cl% C% H% N% 1 50 360 700 8*15 min 56.9% 21.642.54 4*15 min 16*25 min 4*20 min 3*90 min 2*175 min 2 50 360 700 8*10min 85.7% 23.86 2.23 16*170 min 4*90 min 2*80 min 3 50 360 700 4*10 min93.4% 23.74 2.41 16*200 min 2*110 min 5 50 360 700 4*435 min 68.4% 23.822.88 31.4 7.2 18.4 6 50 360 700 4*162 min 31.7% 21.32 1.74 38.1 8.0 13.02*240 min 1*50 min 7 50 360 700 2*420 min 54.9 % 22.60 3.45 34.3 7.514.6 Note: 1. The amount of (NPCl₂)_(n) in each run is 348 g. 2. Flowrate of NH₃ gas: The values in the table are scale values of the flowmeter. The corresponding actual flow rates are:

Scale Actual flow rate Scale Actual flow rate value (ml/min) value(ml/min) 1 82 10 655 2 144 12 720 4 320 14 840 6 428 16 930 8 560 201036

The relationship between the flow rate and the scale value is:

Flow rate=−1.3531x²+78.612x+4.5309, wherein x is the scale value.

According to the content of the phosphorus element and the ratio of theIR absorption peaks in Table 1 and Table 2, the ratio of the IRabsorption peaks shall exceed 60%, and the content of phosphorus isabout 22-24 wt %, when there are two —NH₂ groups in the amino-containingphosphazenes.

A gas chromatograph (GC) was used to measure the relative contents of CBand NPA during the reactions in three experiment runs, and the resultsare listed in Table 3. The data in Table 3 indicate that the reactionsare substantially completed-in five hours. This conclusion conformsnicely with the variation of the IR absorption peaks.

TABLE 3 Tracing the relative content of NPN/CB in the reaction liquid byGC Reaction Reaction one Reaction two Reaction three time (hour) NPA %NPA % NPA % 0 42.75 43.85 36.83 1 34.47 35.10 32.74 2 30.30 32.21 25.743 29.95 23.37 4 32.39 29.49 22.67 5 28.45 21.06 6 31.579 28.99 20.39 720.34 8 9 31.10 28.41 21.14

In order to understand the influence of the flow rate of the NH₃ gas,the solvent, and the amount of Py on the degree of amination of theproduct, more experiment runs were carried out. The results and thereaction conditions are listed in Table 4.

TABLE 4 Ratio of IR Flow rate of absorption NH₃ gas* peaks of Run Py NPAtime CB NH₂OC₃H₇ P% Cl% C% H% N% 1A 80 1000 0 2*420 min <10% 21.13 4.4237.1 7.6 10.8 1B 80 500 500 2*420 min <10% 19.69 4.27 38.7 7.4 10.3 2A80 1000 0 6*420 min 48.4% 21.40 0.67 38.0 82 14.1 2B 80 500 500 6*420min 69.7% 21.54 1.13 36.1 8.0 16.5 3A 160 1000 0 2*420 min 29.0% 19.620.42 42.0 8.5 10.0 3B 80 300 700 6*420 min 73.5% 23.60 1.66 35.5 7.717.1 4A 160 1000 0 6*360 min 41.0% 20.76 0.97 39.41 12.5 8.3 2*60 min 5A240 1000 0 6*360 min 17.1% 19.60 0.40 40.8 8.5 11.0 2*60 min 6A 160 10000 6*360 min 40.0% 20.39 0.44 38.6 8.3 13.0 2*60 min 7A 80 1000 0 8*300min 4*10 min 60.4% 23.06 1.06 33.5 7.8 18.1 2*95 min 8A 80 1000 0 10*240min 6*120 min 63.4% 23.06 1.33 32.3 7.7 18.9 2*60 min 9A 80 1000 0 8*300min 4*25 min 55.5% 22.34 0.66 35.0 8.0 17.4 2*120 min 10A 80 1000 010*160 min 4*80 min 78.6% 22.90 1.38 33.0 7.8 19.0 2*180 min 11A 40 10000 6*420 min 75.0% 23.42 1.30 31.1 7.1 18.6 12B 180 1200 1800 18*360 min70.0% 22.50 1.63 32.4 7.6 19.4 4*60 min 13B 360 2400 3600 20*195 min51.0% 19.56 3.36 39.1 7.2 13.7 15*90 min 10*155 min 14B 360 2400 360025*130 min 68.6% 23.48 1.24 34.0 7.7 18.1 20*210 min 15*20 min 10*60 min15A 80 1000 0 20*250 min 83.0% 23.46 1.72 31.7 7.7 20.1 8*170 minNotes: 1. The amount of (NPCl₂)_(n) used in each run is 348 g.

2. The experiment Run 12B used a 5-liter reaction bottle; the experimentRuns 13B and 14B used a 12-liter reaction bottle; and the rest of theexperiment runs use a 3-liter reaction bottle.

3. The flow rate meter used in experiment Runs 1-12 and 15 is identicalto that used in Table 2. Experiment Runs 1 3B and 14B used another flowrate meter, in which the relationship between the scale and the flowrate thereof is:

Scale Flow rate (ml/min) 10 854 15 1500 20 2180 25 2878

 The relationship between the flow rate and the scale is: flow rate=135.24X−513.2, wherein X is the scale value.

What is claimed is:
 1. A process for preparing a mixture ofamino-containing phosphazenes having the following formula (I):N_(n)P_(n)(NH₂)_(x)(OR)_(2n−x)  (I) wherein n is an integer and n≧3; xis an integer of 1x≦2n; and R is phenyl or C₃-C₆ alkyl, said processcomprising the following steps: a) introducing NH₃ into a reactantmixture comprising HOR, mixed phosphazenes of (NPCL₂)_(n) and a tertiaryamine to undergo reactions at a temperature of 30-100° C. for a periodof time, wherein n is defined as above; b) removing a solid comprisingNH₄Cl precipitate from the resulting reaction mixture from step a) by asolid-liquid separation means; and c) removing volatile compounds fromthe resulting liquid from step b) by evaporation to obtain a mixedproduct consisting essentially of amino-containing phosphazenes havingthe formula (I).
 2. The process according to claim 1, wherein R is —C₃H₇alkyl.
 3. The process according to claim 2, wherein the reactant mixtureused in step a) further comprises an organic solvent.
 4. The processaccording to claim 1, wherein the mixed phosphazenes of (NPCl₂)_(n) instep a) comprise 60-70% by mole of phosphazenes where n=3; 10-20% bymole of phosphazenes where n=4; and 10-20% by mole of phosphazenes wheren≧5.
 5. The process according to claim 1, wherein the tertiary amine instep a) is pyridine.
 6. The process according to claim 2, wherein thetertiary amine in step a) is pyridine.
 7. The process according to claim3, wherein the tertiary amine in step a) is pyridine.
 8. The processaccording to claim 7, wherein said organic solvent is chlorobenzene. 9.The process according to claim 6, wherein the reactant mixture in stepa) comprises 100-500 parts by weight of the mixed phosphazenes, 20-150parts by weight of pyridine, and 500-2000 parts by weight of HOC₃H₇. 10.The process according to claim 9, wherein the reactant mixture in stepa) comprises 350 parts by weight of the mixed phosphazenes, 40-80 partsby weight of pyridine, and 1000 parts by weight of HOC₃H₇.
 11. Theprocess according to claim 8, wherein the reactant mixture in step a)comprises 100-500 parts by weight of the mixed phosphazenes, 80-360parts by weight of pyridine, 300-2400 parts by weight of HOC₃H₇, and500-3600 parts by weight of chlorobenzene.
 12. The process according toclaim 9, wherein the reactant mixture in step a) comprises 350 parts byweight of phosphazenes, wherein the part by weight of chlorobenzene isnot less than that of HOC₃H₇.